This invention relates generally to metallic end fittings for flexible, reinforced hydraulic hose and, more particularly, to such end fittings which are crimped in place on the end of the hose and which are particularly adapted for use with large size and very high pressure hose.
Hydraulic hose generally includes an inner liner of rubber or plastic material which is selected particularly for its sealing capabilities and chemical compatibility with fluid to be conducted through the hose, together with an external reinforcing layer which may be of textile material for low pressure hose but generally is of metallic wire for larger diameter and higher pressure hose. This reinforcing layer may be applied by either braiding or spiral wrapping, and may consist of a plurality of layers embedded in or layered with rubber material which may be the same as or different from the liner and serves to lock the braid in place. In addition, the hose may have an outer cover of rubber material to protect the reinforcing layer against rust and corrosion, as well as abrasion, depending upon the environment in which the hose is used. Naturally, the reinforcing layers must be increasingly stronger, and hence thicker, as the hose size increases or the pressure increases, since the reinforcing layer must serve not only to provide hoop strength against the bursting forces from the hydraulic pressure within the hose but also to provide axial tensile strength because of the tensile forces on the hose as a result of the internal pressure.
When such hose is used in hydraulic systems, it is necessary to provide end fittings to make suitable connection with the other parts of the hydraulic system, and such hose end fittings must not only make good sealing engagement with the hose, and particularly the inner liner, to prevent leakage, but also must provide a suitable grip on the reinforcing layer to ensure that the hydraulic internal forces, as well as any external forces, prevent axial separation of the end from the hose. Generally, such hose end fittings include an insert which extends within the liner of the hose as well as a sleeve or collar that extends over the outside of the hose, and the insert and the sleeve must be compressed radially toward each other to provide the necessary mechanical grip on the hose. The hose fitting also includes an end fitting portion which may have threads or any other suitable construction for making connection with the rest of the hydraulic circuit and which is usually an integral part of the insert to provide hydraulic continuity within the interior of the fitting.
Such hose end fittings are generally of two different kinds. One kind, generally called the "reusable type" fitting, is made for assembly on the hose end in the field with a minimum of tools, and because of the specialized nature of such fittings, they are generally high in cost, although if the hose end is damaged, they may be taken apart, separated from the damaged hose, and assembled again on a new piece of hose. However, a much more common type of hose end fitting is the "permanently attached" type, which is secured on the hose end by plastic deformation of various parts, usually the outer sleeve, of the metal fitting, which heretofore has required large and expensive machinery suitable only for use at main assembly plants.
Thus, it has generally been a decision to use a high-priced reusable type fitting if it is expected that the hose will require replacement in the field, since the use of factory-assembled, permanent type hose ends requires that the entire assembly of the hose and the fitting at each end be replaced, which is complicated because of the variations in the type of end fitting, type of hose, and length of hose, depending upon the particular application of the hose assembly.
To overcome these problems, there are now available relatively inexpensive and portable machines for crimping permanent type hose ends on the hose by the use of a hydraulically powered unit, which, together with conical camming surfaces, causes multiple die section segments to move radially inwardly to crimp the outer sleeve of the hose end in place on the hose. Because such machines are inexpensive and relatively portable, they can be used by dealers and jobbers to provide easy and rapid assembly of hose ends on hoses of any length, and may even be used in the field by customers having sufficient need for manufacturing their own replacement hose assemblies.
However, there has been a problem with these hose assembly machines in that they are generally adapted only to relatively smaller size hose ends, particularly when high and very high pressure hose is used, because the amount of physical force they can apply in crimping a hose end in place is somewhat limited. This is because with larger sizes and with heavier reinforcing layers it is necessary to thicken the wall of the sleeve so that after crimping has taken place, it has sufficient rigidity to be able to maintain a tight grip on the braid. Thus, because of changes in dimensions of different types of hose, each hose end assembly is specifically designed for use with a particular type of hose with regard to dimensions and type of braid layer as well as hose diameter.